The present invention generally relates to bus control units, and more particularly relates to a circuit for activating a control unit by way of a CAN bus.
Generally all electric and electronic control units, ESP sensors or other components are interconnected by way of a standardized CAN (Car Area Network) bus in modern vehicles. The mutual communication of these units is organized by way of a central CAN bus controller, wherein one CAN computer for producing a corresponding data protocol and one CAN bus transceiver, by which the unit is connected to the CAN bus, is associated with each unit.
When the vehicle is not in operation, the CAN bus and the mentioned units are completely or partly inactive, i.e., they are in a sleeping condition and become fully active again only after the ignition is switched on. However, it has proved desirable to be able to activate certain units, such as the ABS control device, also when the ignition is switched off, namely by release of the central locking system or by a xe2x80x98wake-up signalxe2x80x99, produced in any other fashion.
An object of the present invention is to provide a circuit of the type mentioned hereinabove by which a control unit (such as an ABS controller, or another control unit, or also ESP sensors, etc.) can be activated in a defined and reliable manner by way of the CAN bus when the ignition is turned off.
This object is achieved by a circuit comprising a first input for a logic activation signal for the control unit, an input filter for suppressing disturbing pulses in the activation signal, and a device for producing an output signal that activates the control unit when a predeterminable number of activation signals is sensed within a predeterminable duration.
A special advantage of this solution includes that an inadvertent activation by disturbing signals is almost precluded. Further, the circuit can be achieved with a small number of logical construction elements so that the energy consumption may be kept very low.